A launch by lethal loons: North Korea’s Unha-3 rocket lifting off last week — a test that presages ICBM capabilities. Photo: AP

East Asia is in flux: Japan elected a new, more nationalist prime minister over the weekend. China’s new leadership is settling in, as is North Korea’s hereditary Stalinist dictator. And South Korea may elect its first woman president tomorrow.

All the powers in the region have been testing each other and the world, yet America is hardly paying attention — even though President Obama has long pointed out that America’s economicfuture and our most vital interests all lie in the Pacific.

Last week Tokyo scrambled fighter jets after a Chinese plane was seen near the East China Sea islands Japan calls Senkaku (Diaoyu in Chinese) — yet another escalation in the region’s tense island wars.

Then on Sunday Japan elected Shinzo Abe as prime minister. The nationalist candidate has promised to change the pacifist stance that Japan has practiced since the end of World War II.

Tokyo has already become more assertive in the island disputes. Now Abe is expected to further toughen Japan’s response to any perceived provocation to national interests.

In South Korea, conservative candidate Park Geun-hye, a scion of a political dynasty, has a slight lead in polls over liberal Moon Jae-in of the Democratic United Party. Park’s victory (besides being a major boon for women in a chauvinistic society) would assure further toughening of Seoul’s regional stance.

In power these last few years, her party (now know as Saenuri) had already grown more assertive with North Korea. And South Korean voters couldn’t have missed the weekend launch by that neighbor of a long-range Unha rocket.

Yesterday, subjects in the North bowed their heads in unison to commemorate the first anniversary of the death of Kim Jong-il. During the year his son, Kim Jong-un, managed to purge from power some of dad’s closest military allies.

But he’s no reformer. Young Kim continues the family tradition: When in doubt, threaten the neighborhood and the world. And this new leader now has more dangerous toys to play with than his father and grandfather ever had. Sooner or later (absent regime change), the North could endanger parts of the United States.

Even now, Kim can easily end the world order as we know it: Truck a “dirty bomb” over to the 38th parallel, wait for the right wind and detonate. All possibility of good life in the economic powerhouse of South Korea will surely be gone.

In China, Xi Jinping is consolidating power after being named Communist Party chief last month — and he’s not expected to back down either. In fact, recent maneuvering suggests that Beijing is likely to push the envelope at every turn. Xi clearly intends to test the region, feeling his way around China’s shift from a mere world economic powerhouse to a certified global leader.

Perhaps the increasingly rambunctious region will wind up with a peace dominated by China; call that Option A.

Here’s Option B: The Pacific becomes a laboratory for the theories of Thomas Hobbes, with everyone jumping at everyone else’s throat.

Or C: After initial muscle-flexing, the new crop of East Asian leaders all decide that too much money is involved, and that for business to flourish everyone needs to live in peace, love and understanding. (Hey, Christmas is around the corner.)

There’s another option. President Obama even has a name for it, one touted in government position papers and studied by top foreign-policy academics: America’s “pivot” to the Pacific.

But as Washington endlessly haggles over budgets, it seems to keep cutting mostly from the Pentagon. Soon, there’ll be nothing left to “pivot” with.

Plus, Obama looks set to man his national security team with Sens. John Kerry and Chick Hagel — both allergic to even the hint of US intervention anywhere.

So Asians who were hoping for some American help in settling island-ownership disputes, or who have relied on the US Navy for defense — even those who hope we’d assure freedom of navigation for all — are more skeptical than ever.

They see us retreating — leaving each Asian country on its own.

Yes, some regional balance will be found in the end (probably after a lot of turmoil and possible bloodletting, and assuming that Kim doesn’t decide to let it all go kaboom first). But with American involvement ever diminishing, who’ll take care of our interests?